1. Field of the Invention
The invention relates to a device for automatically activating a door, in particular a lifting door, which has an essentially vertical opening plane, an inner side and an outer side, and approach areas which are level with the floor and are respectively located on the inner side and on the outer side.
2. Description of Related Art
It is generally known that with automatically activated doors it is necessary to take safety precautions to prevent obstructing objects or persons who are located in the door opening from being damaged or injured when the door is automatically closed.
For this purpose, it has been known to arrange touch-sensitive contact strips on the closing edges of automatically activated doors, which strips deactivated the door drive or reversed it to the opening direction as soon as the respective touch-sensitive contact strip was in contact with an obstructing object or a person located in the door opening.
Another known solution for protecting obstructing objects or persons before a closing, automatically activated door strikes them has been to extend a number of photoelectric barriers across the opening plane of the door or to provide the opening plane of the door with what is referred to as a light curtain by means of a scanning light beam, a signal for deactivating or reversing the drive for the automatically activated door being generated when said curtain is infringed at any point of the part of the opening plane which has not yet been taken up by the closing door. A very advantageous system of this type is described, for example, in U.S. Pat. No. 6,218,940.
Automatically activated doors for very large door openings, for example of aircraft hangars, fire service equipment halls, assembly halls and the like move at comparatively high speed both in the opening direction and in the closing direction, for which reason it may be found that even though an obstructing object which is to be moved to the door opening and has a part, for example the tips of forklift truck prongs, which is near to the floor and extends to the opening plane, infringes the light and brings about the triggering of a detector signal which triggers the deactivation or reversal of the door drive, the deactivation or reversal of the door movement does not take place promptly enough for subsequent, upwardly projecting parts of the obstructing object, which is to be moved onto the opening plane, to be sensed by the closing door and are thus damaged, and in particular also damage the door seriously.
Attempts have been made to counter these problems by installing in addition to a security system which provides a light curtain which extends across the opening plane of the door opening, for example by means of a detector beam or a plurality of detector beams, a further safety system which contains a movement sensor which is installed approximately in the center of the door opening and which directs detector radiation fields onto an approach area in front of the opening plane and whose infringement by an obstructing object which is moving toward the opening plane of the respective door, or by a person who is moving in a corresponding way, causes the automatic door drive to be controlled in the door opening direction. The radiation fields of such movement sensors are fixed in this context.
In these known systems, the proximity sensor which is to be provided in addition to the light curtain which monitors the door opening plane and which monitors approach areas on the inner side of the door or outer side of the door entails additional expenditure on equipment. It has also become apparent that the detector radiation fields of known proximity sensors monitor the respective approach area only in a discontinuous fashion in such a way that, for example, a child can pass through between the monitoring radiation beams and thus reach the opening plane of the closing door without “advance detection”. Finally, movement sensors which are mounted above the opening of the door have the disadvantage that, at a short distance in front of the opening plane, detector beams of the proximity sensor are directed very steeply downward onto the approach area to be monitored and therefore a horizontal speed of an obstructing object which is to be sensed or of a person which is to be sensed only has a very small speed component in the direction of the detector beam, such that movement sensors which operate according to the Doppler principle often have an inadequate sensitivity for the region of the approach area which is located near to the opening plane.
It is to be noted that it is generally known to scan vertical monitored regions, for example the facades of houses or else horizontal monitored regions, for example areas of land, using scanning beams of a laser radar scanning detector and in this way to generate a monitoring signal when the respective monitored region is infringed, said signal being fed to a corresponding evaluation means. Furthermore it is known to generate a light curtain by means of a laser radar scanning detector within a door opening which is located in a vertical plane, a monitoring signal which is used to control the door being triggered by means of the detector when said light curtain is infringed by an obstacle.